M51 Whirlpool Galaxy

[weixing]

Hi,
My first attempt on M51 (Whirlpool Galaxy) took on 12 May 2007 01:37 in Tampines. Make a few mistake, careless and the image were out of focus... So it's stay in my computer till recently when I got more time to process as much as possible to make the image look more decent.

Capture Info
Telescope: Celestron 8" F5 Newtonian
Camera: Canon 300D Prime Focus with Coma Corrector
Location: Tampines, Singapore
Image: 20 x 2 minute Images @ ISO800

The image look a bit greenish due to the light pollution filter. I think it'll be better if I don't put on the light pollution filter... at least eye ball focusing will be a lot easier. Will try again on my next imaging session if M51 is still visible.

Have a nice day.

 

[asterixsg]

Great. Thanks for sharing. These past few nights, the weather has been simply horrible

 

[redstone]

Beautiful! Is this image enhanced?

Sg skies are so light polluted.

 

[weixing]

Beautiful! Is this image enhanced?

Sg skies are so light polluted.

Hi,
Yes, Singapore was very light polluted... most of our electrical energy were wasted by all those poor design lighting which "light" up our beautiful night sky...

Anyway, this image was a result of image processing which is very common in Astrophotography. Basically, the image will goes through the following 2 process: Calibration and Stacking.

The calibration process will mitigate the effect of noise, dust on the camera sensor, vignetting and etc.

The stacking process will increase the signal to noise ratio, so that the noise will be further reduce and the object details will be enhanced.

Also, to reduce the effect of light pollution, I used a light pollution filter which are designed to selectively reduce the transmission of certain wavelengths of light, specifically those produced by artificial light. This includes mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. sky glow). But the light pollution filter also cause the focusing to be very difficult, so I think next time I'll try not to use the light pollution filter and hope I still be able to get decent raw images to process.

Have a nice day.

 

[etegration]

interesting! thanks for sharing.

 

[ericpooi]

Weixing: Just a novice comment... maybe you should prefocus yourshot, then you add the light filter... it might work... anyhow, great picture!!

 

[weixing]

Weixing: Just a novice comment... maybe you should prefocus yourshot, then you add the light filter... it might work... anyhow, great picture!!

Hi,
The filter is mount in front of a coma corrector (use to correct coma in a fast Newtonian telescope) which one end connect to my DSLR and the other end is inserted in the focuser. In order to put the filter, I need to remove the coma corrector together with my DSLR from the focuser. So in-order to maintain focus after I install the filter, I need to place the coma corrector back at the exact distance and position in the focuser... the error must be less than 0.1mm (or 0.2mm at most) for my F5 scope.... a bit too difficult for my low cost scope. That's why I prefer not to touch anything once the scope is focus. Also, the focus position with and without the filter is slightly different and it'll cause it to be out of focus too.

Anyway, I think I might still be able to get a decent RAW image without the light pollution filter. Now waiting for the next clear sky on a weekend night.

By the way, below is the reprocessed image:

Have a nice day.

 

[codling]

i marvel at the great pics...but just want to ask whats the total cost of your stargazing equipment, sans your dSLR.
did a rough check, your newtonian cost US$1k?

 

[weixing]

i marvel at the great pics...but just want to ask whats the total cost of your stargazing equipment, sans your dSLR.
did a rough check, your newtonian cost US$1k?

Hi,
Not quite sure how much I spend for all of my equipment as I get it over the years and most of them are used equipment. I think the price you quote comes with a computerize mount. Anyway, I got my Newtonian (mount not included as I already have a mount) from the used market in Singapore... I think around S$500. You can visit Singapore Astronomy Forums (SingAstro - http://www.singastro.org/ ) if you are interested in stargazing.

Have a nice day.

 

[Hydrogen]

do you have a motor on the telescope to correct for earth's movement?

 

[weixing]

do you have a motor on the telescope to correct for earth's movement?

Hi,
Yes. I used a motor drive to compensate the earth rotation. It's work quite well and allow me to take 1 to 2 minutes of exposure with very little or no star trail at 1000mm focal length, but you need to do very accurate polar alignment (aligned to north in Singapore)

Have a nice day.